Polymers and copolymers of, and surgical devices made from, lactide and/or glycolide and/or related compounds are well-known. See, e.g., U.S. Pat. Nos. 2,668,162, 2,683,136, 2,703,316, 2,758,987, 3,225,766, 3,268,486, 3,268,487, 3,297,033, 3,422,181, 3,442,871, 3,463,158, 3,468,853, 3,531,561, 3,565,869, 3,597,449, 3,620,218, 3,626,9478, 3,636,956, 3,736,646, 3,739,773, 3,772,420, 3,773,919, 3,781,349, 3,784,585, 3,792,010, 3,797,499, 3,83,297, 3,846,382, 3,867,190, 3,875,937, 3,878,284, 3,896,802, 3,902,497, 3,937,223, 3,982,543, 4,033,938, 4,045,418, 4,057,537, 4,060,089, 4,137,921, 4,157,437, 4,243,775, 4,246,904, 4,273,920, 4,275,813, 4,279,249, and 4,300,565, U.K. Pat. or Appln. Nos. 779,291, 1,332,505, 1,414,600, and 2,102,827, D. K. Gilding et al., "Biodegradable polymers for use in surgery--polyglycolic/poly (lactic acid) homo-and copolymers: 1," Polymer, Volume 20, pages 1459-1464 (1979), and D. F. Williams (ed.), Biocompatibility of Clinical Implant Materials, Volume II, chapter 9: "Biodegradable Polymers" (1981). Multi-phase polymeric compositions are shown in Matsuo et al., "Fine Structures of Styrene-Butadiene Block Copolymer Films Cast from Toluene Solution," Polymer, Volume 10, pages 79-87 (1969). All of the foregoing documents are hereby incorporated by reference.
Some of those documents mention or discuss making lactide/glycolide/related compound polymers or copolymers of small particle size. See, e.g., U.S. Pat. Nos. 3,781,349 and 3,846,382.
Some of those documents mention or discuss multi-stage or sequential addition of monomers in making the lactide/glycolide/related compound polymers or copolymers. See, e.g., U.S. Pat. Nos. 3,268,486, 3,268,487, 3,784,585, 4,137,921, 4,157,437, 4,242,775, and 4,300,565.
Some of the documents first listed mention or discuss multi-phase or block systems containing the lactide/glycolide/related compound polymers or copolymers. See, e.g., U.S. Pat. Nos. 3,268,486, 3,268,487, 3,463,158, 3,773,919, 3,784,585, 3,875,99 4,045,418, 4,057,537, 4,137,921, 4,157,437, 4,243,775, 4,279,249, and 4,300,565, U.K. Pat. No. 1,332,505, Gilding et al., and Williams.
Some of the documents first listed mention or discuss annealing, heat-treating, or post-treating surgical articles containing the lactide/glycolide/related compound polymers or copolyemers. See, e.g., U.S. Pat. Nos. 3,422,181, 3,626,948, 3,636,956, 3,772,420, 3,792,010, 3,797,499, 3,839,297, 3,878,284, 4,137,921, 4,157,437, 4,243,775, and 4,300,565, and U.K. Pat. or Appln, Nos. 1,332,505, 1,414,600, and 2,102,827.
In particular, some of the documents first listed mention or discuss annealing, heat-treating, or post-treating surgical articles made of poly(lactide/glycolide) copolymers made by multi-stage or sequential addition of the monomers. See, e.g., U.S. Pat. Nos. 4,137,921, 4,157,3437, 4,243,775, and 4,300,565. In those documents, glycolide moieties constitute more than 50% by weight of the lactide/glycolide copolymers.
It is known that annealing polymers, copolymers, and surgical devices made from lactide and/or glycolide and/or related compounds increases the crystallinity and in vivo tensile strength retention of the polymers, copolymers, and surgical devices. It is also known that the greater the crystallinity, the longer such polymers, copolymers, and surgical devices retain their in vivo tensile strength. See some of the documents first listed, e.g., U.S. Pat. Nos. 3,636,956 (particularly column 2, line 43 et seq.), 4,137,921 (particularly column 9, lines 61-64), U.K. Appln. No. 2,102,827, and Williams (particularly pages 222-224). It is also known that increasing the crystallinity of such polymers and copolymers makes them more brittle and, thus, decreases their utility as injection molded surgical devices.